Develop a Simple Bulk SMS Application

I want to create a software solution that lets community organizers, buisnessmen and leaders use a low-cost bulk sms tool with opt-in through a simple online form or short code, well organized groups, threated responses and archived messages. This is a simple web application that will allow users to send and coordinate large numbers of SMS messages. There must be excel intergration and online payment. SMS messages can be sent to numbers on many carriers in the form 123456789@[login to view URL] where [login to view URL] is specific to the carrier. This is the method I am currently favoring, but if you know of another method of similar cost I'm open to it. As long as the baseline functionality is the same, I'm open to suggestions regarding features and functionality.